1. Field of the Invention
The present invention relates to an electron beam apparatus used as an image forming apparatus, such as a panel-type image display apparatus, an image recording apparatus, or the like, and more particularly, to an electron beam apparatus using a spacer covered with a high-resistance film in which a very small current can flow, and a method for manufacturing the spacer.
2. Description of the Related Art
In general, a panel-type electron beam apparatus has a configuration in which a first substrate having electron emitting elements and wires for driving the electron emitting elements, and a second substrate having a conductive member that is set to a potential different from a potential of the wires, face each other with a spatial interval separating the substrates. The circumference of the first and second substrates is sealed. In order to obtain a necessary atmospheric pressure-resistant property, an insulating spacer is inserted between the first and second substrates. However, there is a problem that the spacer can become charged so as to deviate an electron emission position by influencing an electron trajectory near the spacer, thereby tending to cause, for example, a decrease in the luminance of a pixel near the spacer, or a degradation of an image, such as color mixture, or the like. The conductive member of the second substrate is used, for example, as an acceleration electrode for accelerating electrons emitted from an electron emitting element. Since a high voltage is applied to the conductive member, charging of the surface of the spacer may cause creeping discharge.
It has been known that, as described in Patent Literature 1 referred to below, charging of the surface of the spacer is prevented by causing a very small current to flow in the spacer. More specifically, a high-resistance film, serving as a charging preventing film, is formed on the surface of the insulating spacer, the high-resistance film is connected to wires on the first substrate and the conductive member of the second substrate via a low-resistance conductive member, and a very small current is caused to flow in the surface of the spacer. The low-resistance conductive member is formed on the contact surfaces between the spacer, and a faceplate and a rear plate.
It is also known that, as disclosed in Patent Literature 2 referred to below, by providing at least one low-resistance electrode for deflection or convergence of an electron trajectory on the surface-of the spacer, an electron trajectory near the spacer can be controlled by controlling the potential of the electrode.
Patent Literature 1: U.S. Pat. No. 5,760,538
Patent Literature 2: U.S. Pat. No. 5,859,502
However, the above-described conventional techniques have the following problems.
That is, when a low-resistance portion, such as an electrode, is formed on the surface of the spacer, and the positional relationship between the spacer and an electron emitting element near the spacer deviates from a desired position, since the distribution of the electric field near the spacer greatly changes, an electron trajectory near the spacer changes, thereby sometimes causing deviation in the position of arrival of an electron beam. Such deviation of the positional relationship between the spacer and the electron emitting element may occur, for example, when the installment position of the spacer deviates from a predetermined desired position, when the spacer is inclined, or when the shape of the base material of the spacer differs from a desired shape.
In order to suppress the above-described deviation of the position of arrival of the electron beam, for example, it is necessary to (a) suppress variations of the electric-field distribution to a position deviation that does not greatly influence the electron trajectory by improving the accuracy in the installment position of the spacer during manufacture of an electron beam apparatus, (b) improve the accuracy in processing of the base material of the spacer, or (c) improve the accuracy in the position of an electrode formed on the spacer surface. Deviation in the position of arrival of an electron beam can also be suppressed by controlling the electron trajectory by appropriately adjusting the potential of an electrode formed on the spacer surface in accordance with deviation of the position of the spacer.
However, these methods will cause a complicated manufacturing process, a decrease in the production yield, or complicated control of the apparatus, resulting in an increase in the production cost. Even if assembly with high accuracy is performed, it is often difficult to prevent deviation of the position at a subsequent heat process, or the like. Furthermore, when the relative position with a near electron emitting element is not constant within one spacer, for example, when the spacer has the shape of a rib or a plate, is bent in the longitudinal (long-axis) direction, or is not parallel, the influence of the spacer sometimes cannot be completely removed according to the above-described methods.